Somatosensory evoked potentials associated with tactile stimulation at detection threshold in man.

Somatosensory evoked potentials elicited by sub- and supraliminal tactile pulses were studied during continuous threshold measurement. Two threshold methods were used: a modified tracking method and a detection method. With both methods threshold estimates of the same order of magnitude were obtained. Stimuli just above the threshold elicited a distinct somatosensory evoked potential with components P50, P100, N190 and P400. No such SEP was associated with the subliminal stimuli. However, in some cases some potential oscillations were obtained, time-locked to the subliminal stimuli; these are suggested to be due to errors in responding. In control experiments detected stimuli elicited a distinct SEP, but no SEP was associated with undetected stimuli of identical amplitude.